1. Field of the Invention
The present invention relates to a communication device composed of a plurality of units, and in particular, to the mounting structure of the respective units.
2. Related Art
FIG. 1 is a layout diagram of respective. units in a conventional communication device. FIG. 2 is a schematic perspective view of the conventional communication device. Hereinafter, explanation will be given based on these Figures.
A conventional communication device 50 is so configured that two transmission/reception units 521 and 522 of transmission systems for performing transmission and reception with the same polarized wave, a modulation/demodulation unit 54, two branching units 531 and 532, and line switching and monitor control unit 55 are accommodated in one casing 51.
Next, the arranging relationship among these units will be described. The transmission/reception units 521 and 522 and the branching units 531 and 532, consisting of components which differ depending on the selected radio frequency, are arranged in the upper part of the casing 51, and the modulation/demodulation unit 54 and the link switching and monitor control unit 55, consisting of the same components irrespective of the radio frequency, are spaced apart from each other and arranged in the lower part of the casing 51.
Further, one branching unit 531 is electrically connected to one transmission/reception unit 521 via a transmission signal line 561, and is electrically connected to the other transmission/reception unit 522 via a reception signal line 571. The other branching unit 532 is electrically connected to the other transmission/reception unit 522 via a transmission signal line 562, and is electrically connected to the one transmission/reception unit 521 via a reception signal line 572. Such a communication device 50 is disclosed in, for example, the Japanese Patent Application Laid-open No. 08-116294 (hereinafter referred to as Patent Document 1).
Here, consideration will be made for the reason why a plurality of units are arranged to be in an arranging relationship shown in FIG. 1. In the initial stage of developing this kind of communication device, the transmission/reception units 521 and 522 were large in their structure. Therefore, a communication device might have either an arrangement that the transmission/reception units 521 and 522 are placed above and the branching unit 531 and 532 are placed below as shown in Patent Document 1, or an arrangement that the transmission/reception units 521 and 522 are placed below and the branching unit 531 and 532 are placed above as shown in FIG. 1. Next, the arranging relationships shown in FIG. 1 and Patent Document 1 will be compared. When comparing the transmission/reception units 521 and 522 and the branching units 532 and 532, maintenance is performed less frequently for the branching units 531 and 532. Accordingly, considering from an aspect of maintenance, the arranging relationship shown in FIG. 1 where the transmission/reception units 521 and 522 are placed below and the branching units 531 and 532 are placed above, is most appropriate, comparing with that of Patent Document 1.
However, in the arranging relationship shown in FIG. 1, the branching units 531 and 532 are placed above the transmission/reception units 521 and 522 with high heating values, whereby the branching units 531 and 532 are exposed to the heat of the transmission/reception units 521 and 522. Therefore, it is required to take such countermeasures as addition of discharging items to the transmission/reception units 521 and 522 or easing of specification circumstance. This leads to a cost increase and a weak product competitiveness.
In order to avoid such a situation, the transmission/reception units 521 and 522 and the branching units 531 and 532 may be arranged in parallel. However, considering the mounting area of the casing 51, it is impossible to enlarge the size of the casing 51. Therefore, it is the current situation that measures against heat must be taken by considering the arranging relationship of the units while keeping the current size of the casing 51.
Further, in the case of the arranging relationship between the transmission/reception units 521 and 522 and the branching units 531 and 532 shown in FIG. 1, the lengths of the transmission signal lines 561 and 562 and the reception signal lines 571 and 572, extending from the branching units 531 and 532 to the transmission/reception units 521 and 522 respectively, are different, whereby a difference of cable loss is caused, which causing a problem that a signal delay occurs between the active transmission system and the standby transmission system. Further, cabling between the active transmission system and the standby transmission system becomes complicated, causing a problem of the high manufacturing cost.